ultra-high sensitivity plasmonic nanosensor based on multiple fano resonance in the mdm side-coupled cavities

We propose a compact plasmonic structure comprising a metal-dielectric-metal (mdm) waveguide coupled with a side cavity and groove resonators. the proposed system is investigated by the finite element method. simulation results show that the side-coupled cavity supports a local discrete state and the groove provides a continuous spectrum, the interaction between them, gives rise to the fano resonance. the asymmetrical line shape and the resonant wavelength can be easily tuned by changing the geometrical parameters of the structure. moreover, we can extend this plasmonic structure by the double side-coupled cavities to gain the multiple fano resonances. the proposed structure can serve as an excellent plasmonic sensor with a sensitivity of ∼1900 nm/riu and a figure of merit of about ∼3.8 × 104, which can find wide applications for nanosensors.